Adult Atlantic Yellow-legged Gulls atlantis may be identified by a combination of factors from other gull species. The list below is provisional. The weighting to be attached to particular factors and the number required for a positive identification is under review. Differentiating features between populations are that the Atlantic gulls have relative to:

A. graellsii

generally heavier appearance around the head and chest;

heavier bills with stubbier tips;

less graceful and distinctly heavier and more ponderous appearance in flight;

broader wings;

less attenuated appearance at rest with tail tip from midway between P6 and P7 to P7 as opposed to P6);

slightly less dark mantle and bluer-grey sheen rather than neutral grey;